I could also have people at my desk looking at my screen as we go over some code or a project plan. Messaging services are for urgent matters which usually have some privileged info. If it’s just a non urgent question or request, send an email so you don’t interrupt people. Biggest issue with messaging services is that they easily abused for things that can done via asynchronous communication. They become big distractions.

Depends on what you want to share. Sometimes it's helpful to have like maybe code and a browser or terminal up to present to someone